Pulse train induced rotational excitation and orientation of a polar molecule.

We investigate theoretically the rotational excitation and field free molecular orientation of polar HBr molecule, interacting with train of ultrashort laser pulses. By adjusting the number of pulses, pulse period and the intensity of the pulse, one can suppress a population while simultaneously enhancing the desired population in particular rotational state. We have used train of laser pulses of different shaped pulse envelopes. The dynamics and orientation of molecules in the presence of pulse train of different shapes is studied and explained.

Controlling rotational dynamics and alignment of molecule by infrared laser pulse.

We investigate the effects of delayed infrared laser (IRL) pulse shape on the non-adiabatic rotational excitation and alignment of a polar molecule. We suggest a control scheme for choosing populations of molecular rotational states by wave packet interference. The rotational wave packets of polar molecule (here HBr) excited non-adiabatically by orienting pulse is controlled actually using the second delayed IRL pulse. By adjusting the time delay between the two laser pulses and the shape of delayed IRL pulse, constructive or destructive interference among these wave packets enables the population to be enhanced or repressed for the specific rotational state. We have used fourth order Runge-Kutta method to study the non-adiabatic rotational excitation (NAREX) dynamics.

Pulse shape effect of delayed pulse on non-adiabatic rotational excitation.

We examine the time evolution of Non-adiabatic excitation of polar molecule in static field exposed to a combination of delayed pulses. The delayed pulse pair consists of half cycle pulse (HCP) and an another delayed pulse (either ultrashort half cycle pulse or zero area pulse). We describe how Non-adiabatic rotational excitation (NAREX) due to Gaussian HCP pulse alone can be greatly modified by applying ultrashort HCP/zero area pulse. It is also shown that non-adiabatic rotational excitation can be controlled by various laser parameters, out of which pulse shape plays the most significant role for controlling the dynamics. Time dependent Schrödinger equation (TDSE) of NAREX dynamics, are studied using efficient fourth order Runge Kutta method.